All right y'all, it's pretty amazing where my cardiovascular physiology journey has taken me. One question leads to an answer and then that answer leads to another question 
Well, I have come to the end of the road, and it's quite a paradox. Where Dr. Guyton's contributions have been a big help in my search for the answer his ideas have now confused me---maybe I, for the last time, turn to the great and brilliant minds of SDN. Following is an article from the 1962 Handbook of Physiology ~Circulation~ by Dr. Guyton when he first introduced the "Guyton analysis" or what we students commonly know as the cardiac and systemic function curves. My focus, however, is on Guyton's analysis of the relationship between increased vasomotor tone and its effect on the vascular function curve.
THE PASSAGE:
"Increased vasomotor tone has been caused by infusion of a sympathomimetic drug [epinephrine]. [As the rate of the sympathomimetic drug infusion was increased, the vascular function curve shifts in a parallel fashion up and to the right exactly like it does in a blood transfusion]....The slope of the venous return curve did not change, which is why it shifted in a parallel fashion. On second thought, one can understand why this is true. When vasomotor tone [arteriolar tone] is increased throughout the circulation while blood volume remains constant, pressures everywhere in the circulation will tend to rise because of tightening of the vessels around the blood. But, if any single segment of the circulation constricts, some other segment of the circulation must dilate. On average, then, for every constriction that occurs in the systemic circulation following the injection of epinephrine, there had to be equal dilation everywhere else. Indeed, measurements have shown that, as the arterioles constrict under these conditions, there is a tendency for the veins to dilate even though the walls of the veins to tighten to a very great extent. This elevates mean systemic pressure but does not increase the resistance to blood flow from the systemic veins toward the heart. In essence, then, we can say that an increase in vasomotor tone effect venous return principally by increasing the mean systemic pressure, and, usually, an increase in vasomotor tone does not increase the average resistance that opposes the return of blood to the heart."
Issue 1)
So do y'all see the problem. To this date ALL texts and board review series books say that an increase in vasomotor tone [which is the same thing as increased TPR] will NOT change the mean systemic pressure because the compliance and volume changes of the arterioles contribute insignificantly to the mean systemic pressure. For this reason, all texts have increased TPR shifting the vascular and cardiac function curve downward, with NO change in mean systemic pressure!
Issue 2)
"But, if any single segment of the circulation constricts, some other segment of the circulation must dilate. On average, then, for every constriction that occurs in the systemic circulation following the injection of epinephrine, there had to be equal dilation everywhere else...Indeed, measurements have shown that, as the arterioles constrict under these conditions, there is a tendency for the veins to dilate even though the walls of the veins tighten to a very great extent."
----What does that mean? All I know is that if the arterioles constrict, then TPR is up---period. The veins dilate at the same time--what?
If that was the case, then vascular function curves as we learn them are full of it. The bottom line is this. If the veins do indeed dilate as the arterioles constrict, the vascular function curve would be WAY different than what is presented to us in text books AND in the classroom. Here is a description of what the vascular function curve should look like in Guyton's scenerio, where the arterioles constrict while the veins simultaneously dilate--in my point of view:
The vascular function curve will move downward in a parallel fashion as a result of venous dilation [or increased venous compliance]. Thus, a lower mean systemic pressure will be reached. The vascular function curve will then rotate in a counter-clockwise fashion about this new mean systemic pressure as a result of the increased TPR. That is how it should look.
Issue 3
So what/why is Guyton talking about folks, when he says:
1)Arteriolar constriction causes a parallel shift upward [like in a transfusion]
2)The veins simultaneously dilate when a segment of the arterioles constrict
3)What does he mean when he says "if any single segment of the circulation constricts". What is "a segment"?
4)increased vasomotor tone [increased TPR] causes a parallel shift upward on the vascular function curve----YEAH THIS IS TOTALLY WRONG
All I know is that only two things cause a parallel shift upward on the vascular function curve and they are as follows--according to recent texts:
1)Increased venous tone [decreased venous compliance]
2)Rapid transfusion of blood
Does it have something to do with the sympathomimetic drug? Or, has Guyton been correct all these years and current physiology professors/authors have simply been misinterpreting him, thus presenting us with false information in books and in the classroom?
Come on experts, this is the last big challenge!
What do you think?
Wow, this is a long one
I love y'all 
Well, I have come to the end of the road, and it's quite a paradox. Where Dr. Guyton's contributions have been a big help in my search for the answer his ideas have now confused me---maybe I, for the last time, turn to the great and brilliant minds of SDN. Following is an article from the 1962 Handbook of Physiology ~Circulation~ by Dr. Guyton when he first introduced the "Guyton analysis" or what we students commonly know as the cardiac and systemic function curves. My focus, however, is on Guyton's analysis of the relationship between increased vasomotor tone and its effect on the vascular function curve.THE PASSAGE:
"Increased vasomotor tone has been caused by infusion of a sympathomimetic drug [epinephrine]. [As the rate of the sympathomimetic drug infusion was increased, the vascular function curve shifts in a parallel fashion up and to the right exactly like it does in a blood transfusion]....The slope of the venous return curve did not change, which is why it shifted in a parallel fashion. On second thought, one can understand why this is true. When vasomotor tone [arteriolar tone] is increased throughout the circulation while blood volume remains constant, pressures everywhere in the circulation will tend to rise because of tightening of the vessels around the blood. But, if any single segment of the circulation constricts, some other segment of the circulation must dilate. On average, then, for every constriction that occurs in the systemic circulation following the injection of epinephrine, there had to be equal dilation everywhere else. Indeed, measurements have shown that, as the arterioles constrict under these conditions, there is a tendency for the veins to dilate even though the walls of the veins to tighten to a very great extent. This elevates mean systemic pressure but does not increase the resistance to blood flow from the systemic veins toward the heart. In essence, then, we can say that an increase in vasomotor tone effect venous return principally by increasing the mean systemic pressure, and, usually, an increase in vasomotor tone does not increase the average resistance that opposes the return of blood to the heart."
Issue 1)
So do y'all see the problem. To this date ALL texts and board review series books say that an increase in vasomotor tone [which is the same thing as increased TPR] will NOT change the mean systemic pressure because the compliance and volume changes of the arterioles contribute insignificantly to the mean systemic pressure. For this reason, all texts have increased TPR shifting the vascular and cardiac function curve downward, with NO change in mean systemic pressure!
Issue 2)
"But, if any single segment of the circulation constricts, some other segment of the circulation must dilate. On average, then, for every constriction that occurs in the systemic circulation following the injection of epinephrine, there had to be equal dilation everywhere else...Indeed, measurements have shown that, as the arterioles constrict under these conditions, there is a tendency for the veins to dilate even though the walls of the veins tighten to a very great extent."
----What does that mean? All I know is that if the arterioles constrict, then TPR is up---period. The veins dilate at the same time--what?
If that was the case, then vascular function curves as we learn them are full of it. The bottom line is this. If the veins do indeed dilate as the arterioles constrict, the vascular function curve would be WAY different than what is presented to us in text books AND in the classroom. Here is a description of what the vascular function curve should look like in Guyton's scenerio, where the arterioles constrict while the veins simultaneously dilate--in my point of view: The vascular function curve will move downward in a parallel fashion as a result of venous dilation [or increased venous compliance]. Thus, a lower mean systemic pressure will be reached. The vascular function curve will then rotate in a counter-clockwise fashion about this new mean systemic pressure as a result of the increased TPR. That is how it should look.
Issue 3
So what/why is Guyton talking about folks, when he says:
1)Arteriolar constriction causes a parallel shift upward [like in a transfusion]
2)The veins simultaneously dilate when a segment of the arterioles constrict
3)What does he mean when he says "if any single segment of the circulation constricts". What is "a segment"?
4)increased vasomotor tone [increased TPR] causes a parallel shift upward on the vascular function curve----YEAH THIS IS TOTALLY WRONG
All I know is that only two things cause a parallel shift upward on the vascular function curve and they are as follows--according to recent texts:
1)Increased venous tone [decreased venous compliance]
2)Rapid transfusion of blood
Does it have something to do with the sympathomimetic drug? Or, has Guyton been correct all these years and current physiology professors/authors have simply been misinterpreting him, thus presenting us with false information in books and in the classroom?
Come on experts, this is the last big challenge!
What do you think?
Wow, this is a long one
I love y'all
